1. Field of the Invention
Embodiments of the invention generally relate to electronic device processing, and more particularly, to vapor deposition processes for tantalum-containing materials and the compositions of the tantalum-containing materials, such as tantalum carbide nitride materials.
2. Description of the Related Art
The electronic device industry and the semiconductor industry continue to strive for larger production yields while increasing the uniformity of layers deposited on substrates having increasingly larger surface areas. These same factors in combination with new materials also provide higher integration of circuits per unit area on the substrate. As circuit integration increases, the need for greater uniformity and process control regarding layer characteristics rises.
Several areas of fabrication that are constantly improving include the formation of metal gate electrodes and the deposition of contact barrier layers. Gate electrodes have often been made with silicon based materials, but more frequently are made with metallic materials, such as tungsten or cobalt. However, the materials used for gate electrodes have lacked accessible or tunable electronic properties by varying the compositions of the contained materials. While tantalum materials have been used as barrier layers, tantalum materials have only been scarcely used for the formation of metal gate electrodes, despite the variety of electronic characteristics available from tantalum materials.
Formation of tantalum-containing barrier layers, such as tantalum, tantalum nitride, and other tantalum materials, in multi-level integrated circuits poses many challenges to process control, particularly with respect to contact formation. Contacts are formed by depositing conductive interconnect material in an opening (e.g., via) on the surface of insulating material disposed between two spaced-apart conductive layers. Copper, tungsten, and aluminum are the most popular conductive interconnect materials, but may diffuse into neighboring layers, such as dielectric layers. The resulting and undesirable presence of these metals causes dielectric layers to become conductive and ultimate device failure. Therefore, barrier materials are used to control metal diffusion into neighboring materials.
Barrier layers formed from sputtered tantalum and reactive sputtered tantalum nitride have demonstrated properties suitable for use to control metal diffusion. Exemplary properties include high conductivity, high thermal stability, and resistance to diffusion of foreign atoms. Physical vapor deposition (PVD) processes are used to deposit tantalum materials as gate electrodes or in features of small size (e.g., about 90 nm wide) and high aspect ratios of about 5:1. However, it is believed that PVD processes may have reached a limit at this size and aspect ratio. Also, the variety of compositions for tantalum materials is very limited when using a PVD process.
Attempts have been made to use traditional tantalum precursors found in chemical vapor deposition (CVD) or atomic layer deposition (ALD) processes to deposit tantalum materials. Multiple CVD and ALD processes are anticipated to be used in the next generation technology of 45 nm wide features having aspect ratios of about 10:1 or greater. Also, ALD processes more easily deposit tantalum materials on features containing undercuts than does PVD processes. Formation of tantalum-containing films from CVD or ALD processes using TaCl5 as a precursor may require as many as three treatment cycles using various radial based chemistries (e.g., atomic hydrogen or atomic nitrogen) to form tantalum materials. Processes using TaCl5 may also suffer from chlorine contaminants within the tantalum material. While metal-organic tantalum precursors may be used to form tantalum materials containing no chlorine contaminants, the deposited materials may suffer with the undesirable characteristic of a high carbon content.
Therefore, there is a need for a process to deposit tantalum-containing materials, such as tantalum carbide nitride, on a substrate, including as a metal gate electrode as well as a barrier layer, while controlling process parameters in order to form predetermined compositions having select electronic properties.